1. Field of the Invention
The present invention relates to an image transfer sheet which transfers an image formed thereon onto a receiving material. More particularly, the present invention relates to an image transfer sheet which transfers an image, which is formed thereon using an image forming apparatus such as electrophotographic copiers, thermal printers and ink jet printers, onto a receiving material such as cloth, canvas, plastics, paper, wood, leather, glass, china, metal and the like. In addition, the present invention relates to a method for forming an image on the image transfer sheet, and a method for transferring an image formed on the image transfer sheet on a receiving material.
2. Discussion of the Background
Recently, a variety of image forming apparatus have been developed and utilized for copiers and printers. These image forming apparatus include, for example, electrophotographic copiers in which a toner image formed on an image bearing member is transferred onto a receiving material, and thermal printers in which an ink image is formed on a receiving material by imagewise heating a thermal transfer recording material or a sublimation thermal transfer recording material. In addition, inkjet printers in which an image is formed on a receiving material by imagewise shooting an aqueous ink or an ink fused by heat are used as image forming apparatus. The images formed by these image forming apparatus are not only used for a purpose of reading or viewing, but also are tried to be applied for various new applications.
As one of these new applications of the images, a method is proposed in which the images are transferred onto an image receiving material such as cloth, leather, canvas, plastics, paper, wood, glass, china, metals or the like. This method is useful for manufacturing a small lot of made-to-order goods having original pictures thereon, such as T-shirts, sweat shirts, aprons, jackets, cups, plates or stained glass, and for manufacturing small lot of pictures duplicated on canvases, which are mainly manufactured for individuals. Currently, since full color copiers are developed and thereby high quality full color images can be easily obtained, the demand for this method is increasing more and more.
An image transfer sheet used for the image forming method in which toner images formed on the image transfer sheet are transferred onto such an image receiving material mentioned above is discussed, for example, in Japanese Laid-Open Patent Publication No. 52-82509. This Publication discloses an image transfer sheet including an adhesive layer, which is formed on a supporter and which consists of an adhesive selected from the group consisting of silicones and fluorine-containing polymers, and an under coat layer, which is formed on the adhesive layer and which consists of a polymer meltable at a relatively low temperature. When a toner image, which has been formed on the undercoat layer of the image transfer sheet, is brought into contact with a receiving material such as cloth etc. while being heated and pressed, the toner image is transferred onto the receiving material together with the undercoat layer.
In Japanese Laid-Open Patent Publication No. 52-82509, the polymer meltable at a relatively low temperature for use in the undercoat layer (which corresponds to the image transfer layer in the present invention) is selected from the group consisting of polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polyvinylidene chloride and their mixtures, compounds, and copolymers. These materials can be preserved at room temperature without causing problems. However, when the materials are preserved at a relatively high temperature (50xc2x0 C.), the undercoat layer softens, resulting in occurrence of a blocking problem in which the undercoat layer and the other surface of the transfer sheet adhere to each other when the sheet is wound like a roll. When a silicone oil is added to the undercoat layer to avoid the blocking problem, the feeding rollers in an image forming apparatus tend to slip, resulting in occurrence of a problem in which the transfer sheet is mis-fed or jammed in the image forming apparatus. Therefore a need exists for an image transfer sheet having a combination of good preservation property and good feeding property.
In attempting to provide such an image transfer sheet, Japanese Laid-Open Patent Publication No. 8-25788 discloses a technique in which a release layer (corresponding to the backcoat layer in the present invention) constituted of a material such as silicone compounds (e.g., silicone copolymers and silicone resin mixtures), and non-silicone compounds such as polyolefins, waxes, alkyd resins, resins having a long chain alkyl group, fluorine-containing resins, and shellac, is formed on the side of the transfer sheet opposite to the side on which the image transfer layer is formed. However, the feeding property of the sheet in image forming apparatus is not considered in this case.
In addition, in this case the image transfer layer has insufficient adhesion with the receiving materials mentioned above. For, example, an image formed on the image transfer layer is transferred on a T-shirt, a problem which occurs is that the image tends to be peeled from the T-shirt after several washing. In particular, when a release material is included in an image transfer layer, the adhesion of the image transfer layer to a receiving material deteriorates. When a release layer including a release material is formed on the backside of the transfer sheet, the release material tends to be transferred onto the image transfer layer depending on the species of the release material because the transfer sheet is typically wound like a roll. Therefore the adhesion of the image transfer layer to a receiving material also deteriorates.
In order to prevent the blocking problem, a technique in which a resin having a high transition temperature is used in an image transfer layer is proposed. However, the adhesion of such an image transfer layer to a receiving material tends to deteriorate, and in addition, the image transfer layer, which has been transferred onto a receiving material, tends to be cracked when a force is applied thereto.
Because of these reasons, a need exists for an image transfer sheet having a combination of good blocking resistance and good fixing property.
Accordingly, an object of the present invention is to provide an image transfer sheet having a combination of good blocking resistance and good fixing property.
Another object of the present invention is to provide an image transfer sheet having good feeding property in image forming apparatus.
Yet another object of the present invention is to provide an image forming method in which an image is formed on the image transfer sheet without causing feeding problems.
A further object of the present invention is to provide an image transfer method in which an image having good fixing property is transferred on a receiving material such as cloth, canvas, plastics, paper, wood, leather, glass, china and metals.
Briefly these objects and other objects of the present invention as hereinafter will become more readily apparent can be attained by an image transfer sheet in which at least an image transfer layer and a surface layer are overlaid on a substrate in this order, wherein the surface layer includes a resin, and wherein the resin has a glass transition temperature (Tg) of from 27 to 100xc2x0 C.
The resin preferably includes a resin selected from the group consisting of polyester resins, acrylic resins, styrene-acrylic resins, and butyral resins.
The surface layer may include two or more resins. In this case, the weighted average glass transition temperature of the resins is from 27 to 100xc2x0 C.
In addition the thickness of the surface layer is from 0.1 to 10 xcexcm.
The image transfer sheet preferably has a backcoat layer on the side of the substrate opposite to the side on which the image transfer layer and surface layer are formed.
In another aspect on the present invention, an image forming method is provided which includes the steps of forming an image formed of a toner on the image transfer sheet mentioned above, and fixing the toner image upon application of at least one of heat or pressure.
The image may be formed of an ink such as a thermofusible ink, a sublimation dye ink or an ink for ink jet printing. When these inks are used for the image, heat and/or pressure are not necessarily applied to the image.
In yet another aspect on the present invention, an image transfer method is provided which includes the steps of preparing an image transfer sheet in which a transfer layer and a surface layer are overlaid on a substrate in this order and in which an image is formed on the surface layer, then bringing the image transfer sheet into contact with a receiving material such that the image contacts the receiving material upon application of heat and pressure, and then peeling the substrate from the image transfer sheet to transfer the image on the receiving material together with the image transfer layer and the surface layer, wherein the image transfer sheet is the image transfer sheet mentioned above.